| MODEL | BSA B1 250 1933 - 1936 |
| Year | 1933 - 1936 |
| Engine Type | Four stroke, single cylinder, side valve |
| Displacement / Capacity | 249 cc / 15.2 cu in |
| Bore X Stroke | — |
| Compression Ratio | — |
| Cooling System | — |
| Max Power | 1.83 kW / 2.49 hp |
| Max Torque | — |
| Ignition | Magneto |
| Induction | Amal, side float carburettor |
| Start System | Slip-on kick starter |
| TRANSMISSION SPECS | |
| Lubrication | — |
| Gear Box | 3-Speed, gearshift mounted on tank |
| Clutch | — |
| Final Drive | Chain |
| CHASSIS SPECS | |
| Frame | — |
| Front Suspension | Girder, spring loaded fork |
| Rear Suspension | None, spring loaded saddle |
| Front Brakes | — |
| Rear Brakes | — |
| DIMENSION SPECS | |
| Overall Length | — |
| Overall Width | — |
| Overall Height | — |
| Seat Height | — |
| Wheelbase | — |
| Ground Clearance | — |
| Dry Weight | — |
| Wet Weight | — |
| WHEEL SPECS | |
| Front Tyre | 2.75 x 19 |
| Rear Tyre | 3.00 x 19 |
| FUEL SYSTEM | |
| Fuel Capacity | — |
| Fuel Consumption | — |
| Top Speed | — |
The B1 was BSA's 1930s 250 cc side-valve single, an economical commuter with a three-speed gearbox shifted by a tank-mounted lever. It kept the girder fork and rigid frame typical of the time, and was a practical entry-level machine.
